1. Field of the Invention
This invention relates to a device and method for separating heavier and lighter fractions of a liquid sample. More particularly, this invention relates to a device and method for collecting and transporting liquid samples whereby the device and liquid sample are subjected to centrifugation in order to cause separation of the heavier fraction from the lighter fraction of the liquid sample.
2. Description of Related Art
Diagnostic tests may require separation of a patient's whole blood sample into components, such as serum or plasma, the lighter phase component, and red blood cells, the heavier phase component. Samples of whole blood are typically collected by venipuncture through a cannula or needle attached to a syringe or an evacuated collection tube. Separation of the blood into serum and red blood cells is then accomplished by rotation of the syringe or tube in a centrifuge. Such arrangements use a barrier for moving into an area adjacent the two phases of the sample being separated in order to maintain the components separated for subsequent examination of the individual components.
A variety of devices have been used in collection devices to divide the area between the heavier and lighter phases of a fluid sample.
The most widely used device includes thixotropic gel materials such as polyester gels. The present polyester gel serum separation tubes require special manufacturing equipment to prepare the gel and to fill the tubes. Moreover, the shelf-life of the product is limited in that overtime globules may be released from the gel mass. These globules have a specific gravity that is less than the separated serum and may float in the serum and may clog the measuring instruments, subsequently during the clinical examination of the sample collected in the tube.
Moreover, while the gel is chemically inert to blood samples, if certain drugs are present in the blood sample when it is taken, there can be an adverse chemical reaction with the gel interface.
Therefore, a need exists for a separator device that (i) is easily used to separate a blood sample; (ii) is non-temperature dependent during storage and shipping; (iii) is stable to radiation sterilization; (iv) employs the benefits of a thixotropic gel barrier yet avoids the many disadvantages of placing a gel in contact with the separated blood components; (v) minimizes red cell film or red cell hang-up of a blood sample; (vi) minimizes cross contamination of the heavier and lighter phases of the sample during centrifugation; (vii) minimizes adhesion of the lower and higher density materials against the separator device; (viii) is able to function in a plastic or glass container; and (ix) can be used with standard sampling equipment.